Cancer patterns among occupational groups that may reflect exposures in the work environment are identified. Study groups are selected because of 1) exposure to established or suspect carcinogens, 2) reports suggesting an unusual cancer experience, and 3) requests by outside institutions. Resources used include employment and death records maintained by companies, labor unions, professional organizations, and government agencies. Investigations completed during the past year include: 1) proportionate mortality studies of petroleum refiners, embalmers, and professional artists, 2) death certificate case-control studies of leukemia and cancers of the brain, bladder, and lung, and 3) cohort mortality studies of industrial chemists. Other investigations underway, but not completed, include cohort mortality studies of workers having exposure to metal fumes, perchloroethylene, pesticides, wood dusts and paints, formaldehyde, taconite, benzene, and laboratory chemicals. Proportionate mortality studies are being conductd among tobacco manufacturers, potters, leather workers, fur dyers, veterinarians, foresters, plumbers, photographers, and millers. Case-control studies are underway to evaluate the role of farm exposures in the origin of leukemia, lymphoma, soft-tissue sarcomas, and multiple myeloma, and of textile manufacturing in cancer of the colon and prostate.